Detection of high explosives is attracting increasing attention due to homeland security, environmental and humanitarian implications. (J. I. Steinfeld and J. Wormhoudt, Annu. Rev. Phys. Chem. 1998, 49, 203). 2,4-Dinitrotoluene (DNT), an inevitable by-product in the manufacturing process of 2,4,6-trinitrotoluene (TNT), has a room-temperature vapor pressure about 20 times that of the latter; therefore, the detection of nitroaromatic explosives is often achieved by detection of DNT. On the other hand, plastic explosives often do not contain nitroaromatics, the detection of which is consequently realized by detection of 2,3-dimethyl-2,3-dinitrobutane (DMNB, an taggant required by law to all the commercial plastic explosives). In the search of more convenient and cost-effective alternatives to the well-trained canines (K. G. Furton and L. J. Myers, Talanta 2001, 54, 487) or sophisticated analytical instruments (P. Kolla, Angew. Chem. Int. Ed. 1997, 36, 801; A. G. Davies, et al., Mater. Today 2008, 11, 18), new molecular, oligomeric and polymeric, and nano-scale materials that are capable of fast and reliable sensing of the above chemicals have recently been identified. (See S. W. Thomas, et al., Chem. Rev. 2007, 107, 1339; S. J. Toal and W. C. Trogler, J. Mater. Chem. 2006, 16, 2871; L. Senesac and T. G. Thundat, Mater. Today 2008, 11, 28; R. Y. Tu, et al., Anal. Chem. 2008, 80, 3458; T. L. Andrew and T. M. Swager, J. Am. Chem. Soc. 2007, 129, 7254; H. Sohn, et al., J. Am. Chem. Soc. 2003, 125, 3821; M. E. Germain and M. J. Knapp, J. Am. Chem. Soc. 2008, 130, 5422; T. Naddo, et al., J. Am. Chem. Soc. 2007, 129, 6978; S. Y. Tao, et al., J. Mater. Chem. 2006, 16, 4521.) Fluorescence redox quenching is often the working mechanism within these systems. (S. W. Thomas, et al., Chem. Rev. 2007, 107, 1339; S. J. Toal and W. C. Trogler, J. Mater. Chem. 2006, 16, 2871). While high to extremely high sensitivity towards nitroaromatic explosives has been demonstrated, detection of DMNB remains a great challenge largely due to its unfavorable reduction potential (−1.7 V vs SCE) and weak binding to the sensory materials because of its three-dimensional molecular structure that lacks of π-π interactions. (S. W. Thomas, J. P. Amara, R. E. Bjork, T. M. Swager, Chem. Commun. 2005, 4572).
Microporous metal organic framework (MMOFs) materials are a new class of zeolite-like crystalline materials that have been shown by recent research to have great potential in a wide spectrum of applications, e.g. molecular storage and separation, catalysis, sensing, etc. (G. Ferey, Chem. Soc. Rev. 2008, 37, 191; M. Vallet-Regi, et al., Angew. Chem. Int. Ed. 2007, 46, 7548; S. Kitagawa, et al., Angew. Chem. Int. Ed. 2004, 43, 2334; D. Maspoch, et al., Chem. Soc. Rev. 2007, 36, 770; 0. M. Yaghi, Nat. Mater. 2007, 6, 92; J. Y. Lee, et al., Adv. Funct. Mater. 2007, 17, 1255; L. Pan, et al., J. Am. Chem. Soc. 2006, 128, 4180; L. Pan, et al., Angew. Chem. Int. Ed. 2006, 45, 616; L. Pan, et al., Angew. Chem. Int. Ed. 2003, 42, 542; L. Pan, et al., Chem Commun (Carob) 2003, 854; K. Li, et al., Adv. Funct. Mater. 2008, 18, 2205). A small number of all the MMOFs discovered so far are luminescent in solid state. (C. A. Bauer, et al., J. Am. Chem. Soc. 2007, 129, 7136). The combination of luminescence and accessible porosity within such materials imparts them with capability of transducing the host-guest chemistry to observable changes in their luminescence and makes them promising candidates for chemical sensing applications. (B. Chen, et al., Adv. Mater. 2007, 19, 1693; K. L. Wong, et al., Adv. Mater. 2006, 18, 1051; D. Tanaka, et al., Chem. Commun. 2007, 3142; C. Serre, et al., Chem. Mater. 2004, 16, 1177). However, to date these MMOF materials have not been reported for detection of explosives.